Laser printers use a coherent beam of light, hence the term “laser printer,” to electrostatically charge discrete portions of an image transfer drum thus attracting a printing agent such as toner. Toner is a mixture of pigment (most commonly black) and plastic particles. The toner becomes electrostatically attracted to a process roller such as a developer roller, which transfers toner to the charged portions of the image transfer drum. The toner is transferred to paper, or other printing medium, as it passes over the rotating image transfer drum. Subsequently, the paper is heated so that the plastic is melted thereby permanently affixing the ink to the paper.
The vast majority of commercially available desktop laser printers include replaceable or removable toner cartridges that incorporate a wastebin assembly and a toner hopper assembly. The wastebin assembly contains the image transfer drum and a toner reservoir for waste toner. The toner hopper assembly holds the toner and has the developer roller rotatably mounted at its toner exit area. To keep the toner from spilling out of the toner hopper, prior art toner cartridges incorporate developer roller seals that are installed in the toner hopper, which act to seal the ends of the developer roller. These developer roller seals are susceptible to being catastrophically displaced due to friction between the seal and the developer roller. Also the prior art developer roller seals are additional parts that must be manufactured and installed into the cartridge, raising development and assembly costs of the cartridge.
Therefore, what is needed is an imaging cartridge that utilizes a developer roller that seals itself against the housing of the toner hopper, eliminating the need for separate developer roller seals.